如何用JavaScript实现类似MySQL GROUP_CONCAT的按属性分组拼接

Got it, let's break down how to replicate MySQL's GROUP_CONCAT behavior in JavaScript for your array—grouping objects by their type and stitching together the description fields with commas. Here are a couple of straightforward solutions:

Basic Solution (includes duplicate descriptions) #

The Array.reduce() method is perfect for this kind of grouping and aggregation. It lets us build up a result object where keys are the type values, and values are the concatenated description strings.

let obj = [
  { "type": "Bedroom", "int_input": 1, "enum_input": 0, "enum_select": "Yes", "description": "Test" },
  { "type": "Bedroom", "int_input": 1, "enum_input": 0, "enum_select": "Yes", "description": "Test1" },
  { "type": "Bedroom", "int_input": 1, "enum_input": 0, "enum_select": "Yes", "description": "Test" },
  { "type": "Bathroom", "int_input": 1, "enum_input": 0, "enum_select": "Yes", "description": "Sink leak" }
];

const grouped = obj.reduce((acc, currentItem) => {
  // If the type isn't in our accumulator yet, initialize it with the current description
  if (!acc[currentItem.type]) {
    acc[currentItem.type] = currentItem.description;
  } else {
    // Append the new description with a comma separator
    acc[currentItem.type] += `, ${currentItem.description}`;
  }
  return acc;
}, {});

console.log(grouped);
// Output:
// {
//   Bedroom: "Test, Test1, Test",
//   Bathroom: "Sink leak"
// }

Solution with Deduplicated Descriptions #

If you want to avoid repeating the same description (like the duplicate "Test" in the Bedroom group), we can use a Set to track unique values before joining them:

const groupedUnique = obj.reduce((acc, currentItem) => {
  if (!acc[currentItem.type]) {
    // Use a Set to automatically handle unique descriptions
    acc[currentItem.type] = new Set();
  }
  acc[currentItem.type].add(currentItem.description);
  return acc;
}, {});

// Convert the Sets back to comma-separated strings
const finalResult = Object.fromEntries(
  Object.entries(groupedUnique).map(([type, descSet]) => [type, Array.from(descSet).join(', ')])
);

console.log(finalResult);
// Output:
// {
//   Bedroom: "Test, Test1",
//   Bathroom: "Sink leak"
// }

Optional: Convert to Array of Objects #

If you prefer the result as an array of objects (instead of a plain key-value object), you can transform the final output like this:

const resultArray = Object.entries(grouped).map(([type, description]) => ({
  type,
  description
}));

console.log(resultArray);
// Output:
// [
//   { type: "Bedroom", description: "Test, Test1, Test" },
//   { type: "Bathroom", description: "Sink leak" }
// ]

内容的提问来源于stack exchange，提问作者learner